Unreadable scanned images

Hello

When working with images, my Mac (on OSX.6.3) has been acting strangely the past couple of days:

1. Most scanned images are no longer readable by iPhoto (V.6.0.6);

2. Images exported from iPhoto are no longer readable by Preview (V.5.0.2);

3. Most images manipulated in Photoshop (Elements, V.8) or Preview then saved as .jpeg to my desktop get corrupted and are not readable after turning the machine off and back on again.

I ran Cocktail and reloaded the scanner driver (Brother DCP-7020). Not much difference.

I believe the only thing that has changed between now and before all this started was some pop-up message upon opening iPhoto saying that my thumbnails needed to be upgraded. I said 'yes' to that, and then all of my images seemingly disappeared... As it turns out, many of the images were redirected to new "Rolls" (folders), but I did lose some of the images that were there, in iPhoto, when I opened the program before "upgrading". Others are corrupted and not readable.

Any ideas as to what might be happening?

Thanks for any advice.